1. Field of the Invention
The present invention relates to a digital image processing device and a method thereof, and more particularly, to an apparatus for blurring a background of an image in a digital image processing device in which an image is photographed with a flash being on and off when a shutter input signal is received one time, the background of the image is blurred through comparison between an image prior to a shutter input and an image during which a flash is active, and then a subject of the image with a flash being off is combined with the blurred background, and a method thereof.
2. Description of the Related Art
Currently popularized digital image processing devices such as digital cameras, camera phones, and smart phones include various kinds of digital devices and process digitalized data, thereby providing functions that are distinguished from analog photographing equipments.
For example, a large amount of memory is purchased to store a large number of images, compared with a conventional film, and a charge coupled device (CCD) replaces film so as to realize high definition images, thereby permitting a sharing of image data with a personal computer (PC) and facilitating image processing.
In addition, more functions, such as automatic control of shutter speed and aperture values, auto focus, image enhancement, and automatic light quantity control, are provided in digital image processing devices than in analog photographing equipment.
However, analog photographing equipment uses natural optical materials and is hand-operated and thus may be preferred, compared to digital image processing devices, when a higher sensitivity is needed.
Accordingly, recently introduced digital image processing devices have the advantages of digital devices along with the functions of conventional analog image processing devices added thereto. That is, advantages of analog devices are added to these recently introduced digital devices, thereby providing various specialized functions beyond the limitations of digital devices.
In addition, due to the wide availability of digital image processing devices, the popularity of photographing has gradually increased and thus the numbers of people who have acquired professional photographing techniques has also increased.
However, such digital image processing devices cannot satisfy the demands of professional users.
For example, when photographing a person, blurring effect (out of focus effect) is mostly used related to using a shallow depth-of-field. However, when an existing digital image processing device is used, such an effect can hardly be noticed due to the limited size of the lens and CCD.
In general, the blurring effect varies according to a size of a circle of confusion (when one point of a subject forms an image through a lens, the image is formed by a circle of points having a size to be seen as points and a predetermined diameter. For large diameters of such circles, the image is seen as being “out of focus” by a human eye. Here, the circle point having a diameter is denoted as the circle of confusion) and the size of the circle of confusion is closely related to depth (the depth of a focus and depth of field).
Thus, the depth varies according to factors such as the size of CCD, aperture values, focal length of a lens, distance between a subject and a camera, and distance between a subject and a background.
Among factors determining the depth described above, an image sensor, aperture values, and focal length of a lens, and excluding the distance between a subject and the digital image processing device, considerably change according to physical specifications of the digital image processing device. According to characteristics of miniaturized digital image processing devices, only a high depth of field can be formed due to small image sensor and small aperture lens, thereby not satisfying the demands of a user who desires a small depth of field through which only the main subject is clear and the background is blurred.
In addition, when a large-sized sensor and lens are employed in a digital image processing device, it affects a yield of a semiconductor process for manufacturing relatively large image sensors and a special design for the large aperture lens is required, thereby increasing a manufacture cost. Also, a size of the digital image processing device increases and also miniaturization of such a digital image processing device is limited.